CBQE-928: add conseq online upgrade test

Change-Id: Ie7422761c071eb64c68094e1cf49d8e07a543273
Reviewed-on: http://review.couchbase.org/24098
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>